Out-of-date doctor's assistant (5)
I believe the answer is:
leech
This might be a double definition.
'out-of-date doctor's' is the first definition.
'leech' can be an answer for 'doctor's' (I've seen this before). I'm not certain of the 'out-of-date' bit.
'assistant' is the second definition.
The definition and answer can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
Can you help me to learn more?
(Other definitions for leech that I've seen before include "and one of his remedies" , "One used to bleed" , "Blood sucker" , "Sucking parasite" , "Blood-sucking worm or parasitical person" .)